Method of manufacturing sheet metal made poly-V pulleys

ABSTRACT

A method of manufacturing precise sheet metal made poly-V pulleys with poly-V grooves, being uniform in thickness of peripheral wall and free of reduction of mechanical strength, by a step of preliminarily forming a lug in the peripheral wall of a cup-shaped blank and thickening the peripheral wall, a step of forming a plurality of V-grooves in a multiple arrangement on this thickened peripheral wall by pressing from both sides with a V-groove preliminary forming roller possessing a plurality of V-grooves forming ridges and a rotary inner die possessing a plurality of V-grooves while rotating the cup-shaped blank, and a step of pressing this peripheral wall with a plurality of V-grooves with a finishing roller. Furthermore, a method of manufacturing sheet metal made poly-V pulleys having advanced precision, by a step of preliminarily forming lugs and first grooves in the peripheral wall of a cup-shaped blank, and a step of thickening the peripheral wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of manufacturing a sheet metal poly-Vpulley having a plurality of V-grooves arranged at a fixed pitch on theperipheral wall thereof from a sheet metal blank.

2. Prior Art

Since a poly-V pulley generally makes it necessary for a plurality ofridges formed on the poly-V belt to engage with V-grooves, the accuracyof each V-groove is vigorously demanded in the order of 5/100 mm. It ishence required that the pitch, width, and diameter of each V-groove befinished to close tolerances.

In an attempt to meet such demand, the applicant has already proposed amethod of manufacturing a sheet metal made poly-V pulley in JapanesePatent Application No. 54-113820, wherein a plurality of V-grooves areformed on a cup-shaped blank by effecting rolling process by V-groovepreliminary forming roller and compression process in the axialdirection at the same time.

Said method is an improvement of a prior art proposed in U.S. Pat. No.3,977,264, wherein a plurality of V-grooves are formed by folding acup-shaped blank in the axial direction.

In other words, this is a method of forming specified poly-V grooves bypressing the peripheral wall of a cup-shaped blank formed from a sheetmetal blank by deep drawing by means of a corrugating roller from theouter side thereof to corrugate the peripheral wall in a wavy section,compressing said cup-shaped blank in the axial direction while rotatingwith a V-groove preliminary forming roller movable in the axialdirection being pressed to each bottom of the corrugated surface, andpressing a finishing roller to thus formed V-grooves while rotating thecup-shaped blank.

According to this method, therefore, as compared with the methodproposed in said U.S. Publication, the pitch of poly-V grooves can bemade uniform, and since the peripheral wall is not forcedly folded inthe axial direction when forming V-grooves, the uneven biting whichoften occurs in the peripheral wall of cup-shaped blank conventionallymay be eliminated. Moreover, since pattern-drawing or parting from themold is easy, the manufacturing process may be simplified, defectives ornon-conforming products may be reduced, and the sheet metal made poly-Vpulley with improved quality can be presented.

However, in the case of this method, since it is required to fold byapplying compression in the axial direction to the corrugated peripheralwall when forming V-grooves, uneven folds 9 were occasionally formed asshown in FIG. 17 in the V-grooves, and the wall thickness becomesthinner than the other parts in the poly-V groove 3 of a finished poly-Vpulley product, thereby lowering the mechanical strength of the poly-Vpulley, which has caused the inventor of this application to recognizethe existence of further problems to be improved.

SUMMARY OF THE INVENTION

In order to overcome the above-discussed problem, it is a primary objectof this invention to provide a novel method of manufacturing a sheetmetal made poly-V pulley which makes it possible to eliminate aforesaiduneven folds at the time of forming V-grooves, keep the thicknessbetween poly-V grooves equal to that of other parts, and preventreduction of mechanical strength.

It is another object of this invention to provide a method ofmanufacturing a sheet metal made poly-V pulley which makes it possibleto prevent reduction of thickness of a peripheral wall and reduction ofmechanical strength in the process of forming poly-V grooves in aperipheral wall of a cup-shaped blank by thickening the peripheral wallof the cup-shaped blank beforehand.

It is a further object of this invention to provide a method ofmanufacturing a sheet metal made poly-V pulley which is shortened in thetime required for manufacture and is suited to mass producibility.

In order to achieve these objects, according to the first invention ofthe present application, a sheet metal blank is processed in thefollowing processes so that a sheet metal made poly-V pulley ismanufactured.

In other words, a curvature is formed on the peripheral wall of acup-shaped blank formed by deep drawing of a sheet metal blank(hereinafter called as "preliminary first process").

Then, while rotating and axially compressing said cup-shaped blank, theabove curved peripheral wall is pressed by means of an auxiliary formingroller having a lug forming concave portion, and a lug is preliminarilyformed on the peripheral wall of cup-shaped blank, and the thickness ofthe peripheral wall of cup-shaped blank is increased or thickened at thesame time (hereinafter called as "preliminary second process").

Afterwards, while holding the cup-shaped blank in a rotating innerpattern, a plurality of V-grooves are formed in a multiple arrangementon said thickened peripheral wall by squeezing with a V-groove formingroller possessing a plurality of V-groove forming ridges located at theouter side of said peripheral wall and the rotating inner patternpossessing a plurality of ridges located at the inner side of saidperipheral wall (hereinafter called as "V-groove forming process").

Finally, while rotating the cup-shaped blank, thus formed pluralV-grooves are pressed by a finishing roller to be finished into poly-Vgrooves ( hereinafter called as "finishing process").

In the second invention of this application, it is an object, inaddition to the aforesaid objects, to provide a method of manufacturinga sheet metal made poly-V pulley which makes it possible to form poly-Vgrooves at a higher precision.

In order to achieve said object, the second invention provides amanufacturing method wherein a curvature is formed in the peripheralwall of cup-shaped blank, a lug and first grooves are preliminarilyformed in the peripheral wall of cup-shaped blank and the thickness ofthis peripheral wall is increased at the same time by pressing thuscurved peripheral wall by means of an auxiliary forming rollerpossessing lug forming concave portions and first groove preliminaryforming ridges located beneath said lug forming concave portions, whilesupporting the inner wall of this cup-shaped blank in a rotary inner dieand rotating and axially compressing it, and a plurality of V-groovesare formed in a multiple arrangement in thus thickened peripheral wallby pressing with a V-groove preliminary forming roller possessing aplurality of V-groove forming ridges while rotating the cup-shaped blankmaterial, then finally these plural V-grooves are pressed by a finishingroller possessing a plurality of finishing V-grooves while rotating thecup-shaped blank, thereby forming poly-V grooves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a to FIG. 1e illustrate the manufacturing process of the firstinvention of the present application, showing partially cut-awaylongitudinal sectional views of a cup-shaped blank processed andtransformed as a result of embodying the first invention;

FIG. 2a to FIG. 2c are sectional views showing the apparatus to be usedin the embodiment of the preliminary first process of the firstinvention;

FIG. 3 is a partial sectional view of the principal part showing thepreliminary second process of the first invention together with itsapparatus;

FIG. 4 is a partial sectional view of the principal part showing theV-groove forming process of the first invention together with itsapparatus;

FIG. 5 is a partial sectional view of the principal part showing thefinishing process of the first invention together with its apparatus;

FIG. 6 is an enlarged view of part A in FIG. 2a;

FIG. 7 is an enlarged view of part B in FIG. 3;

FIG. 8 is an enlarged view of part C in FIG. 4;

FIG. 9 is an enlarged view of part D in FIG. 5;

FIG. 10a to FIG. 10f are partially cut-away views of a cup-shaped blankin the manufacturing process sequence showing another embodiment of thefirst invention;

FIGS. 11 to 13 show the preliminary second process showing a furtherembodiment of the first invention, wherein

FIG. 11 is a partially cut-away longitudinal sectional view of a formedcup-shaped blank;

FIG. 12 and FIG. 13 are partial sectional views showing the preliminarysecond process sequentially together with its apparatus;

FIG. 14 is a partially cut-away longitudinal view of a cup-shaped blankformed in the preliminary second process of a second invention;

FIG. 15 is a partial sectional view showing the preliminary secondprocess of the second invention together with its apparatus;

FIG. 16 is an enlarged view of part E in FIG. 15;

and FIG. 17 is a partially cut-away longitudinal sectional view of asheet metal made poly-V pulley manufactured in a known method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1a to FIG. 1e sequentially show the changes in shape of acup-shaped blank formed in the manufacturing processes of the firstinvention.

In other words, FIG. 1a shows a partially cut-away longitudinalsectional view of a cup-shaped blank 1. FIG. 1b to 1e show eachsectional structure of blank 1 varied according as it undergoes thepreliminary first process, preliminary second process, V-groove formingprocess, and finishing process.

FIG. 2a to FIG. 2c refer to an example of the equipment used in applyingthe cup-shaped blank 1 to the preliminary first process.

More specifically, FIG. 2a shows the apparatus used in forming acurvature bulging out of a peripheral wall 10 of the cup-shaped blank 1,and FIG. 6 is an enlarged view of part A in FIG. 2a.

In these drawings, numeral 401 denotes a supporting internal die, 402and 404 are outer dies having recesses 402a, 404a corresponding to thecurvature part 11a to define the shape of curvature part 11a to beformed on the peripheral wall 10 of the cup-shaped blank, and 403 is anupper pressing die to press the cup-shaped blank 1 from above togetherwith the outer die 402.

FIG. 2b shows the apparatus used in forming a curvature part 11b beinginward concave in the peripheral wall 10 of the cup-shaped blank 1, andthe parts corresponding to those in FIG. 2a are given same numericalcodes.

In this apparatus, an inner die 401' possesses the shape correspondingto the lower part of the curvature part 11b formed inward in theperipheral wall 10 of the cup-shaped blank 1.

FIG. 2c refers to the apparatus used in forming a curvature part 11c inthe peripheral wall 10 of the cup-shaped blank 1 by using waterpressure. In this drawing, numerals 405 and 406 are upper and lowercompanion dies, 407 is a middle support die, and 408 is a pressurizingpiston, wherein the peripheral wall 10 of the cup-shaped blank 1 bulgesoutward as the water 5 filling its internal cavity is pressurized by thepiston 408 so that the curvature part 11c is formed.

As shown in these drawings, the preliminary first process is to formcurvature parts 11a, 11b, 11c which bulge either inward or outward ofthe peripheral wall 10 of the cup-shaped blank 1, and as a result ofexecuting such preliminary first process, the thickness of theperipheral wall 10 of the cup-shape blank 1 may be increased easily andwithout trouble in the next process.

As the apparatus to be used in execution of such preliminary firstprocess, many other devices than shown in the drawings may be used as amatter of course, but the constitution as shown in FIG. 2a isparticularly advantageous because the peripheral wall 10 can be securelyprojected outward to form a desired curvature part 11a, the cost of theapparatus is lower than that of the apparatus in FIG. 2c, and thecup-shaped blank 1 forming the curvature part 11a may be easily andquickly parted from the die.

FIGS. 3 and 7 illustrate the state of execution of the preliminarysecond process together with its apparatus.

In these drawings, numeral 601 denotes a rotary inner die which isinserted into the inner cavity of the cup-shaped blank 1 so as tosupport the inner wall of the cup-shaped blank 1, and this inner die 601is affixed to a lower support die 602 and it rotates while holding thecup-shaped blank 1, during the execution of preliminary second process,in collaboration with an upper pressing die 604 possessing a concavepart 604a, by rotating a turntable 603 affixed to the lower part of thelower support die 602.

Numeral 605 refers to an auxiliary forming roller which is used topreliminarily form a lug 13 in the peripheral wall having a curvaturepart 11a (or 11b or 11c) of cup-shaped blank 1 and also to thicken theperipheral wall. This roller 605, as is more explicitly shown in FIG. 7,is composed of a concave part 605a for preliminarily forming the lug 13in the cup-shaped blank 1 and a smooth plane 605b for flatly pressingsaid curvature part of the cup-shaped blank 1, and this auxiliaryforming roller 605 is advanced to the side of the curvature part 11a (or11b or 11c) of the rotating cup-shaped blank 1 to press the peripheralwall having said curvature part, while by applying a compressive forcein the axial direction of the peripheral wall by the upper pressing die604 from above at the same time, the lug 13 is preliminarily formed onthe peripheral wall of the cup-shaped blank 1 and the peripheral wall isthickened at the same time.

Thus, when the peripheral wall of the cup-shaped blank 1 is increased inthickness, it is effective to prevent the peripheral wall from becomingexcessively thin in the subsequent V-groove forming process andfinishing process so that a lightweight, material-saving, and strongproduct may be obtained.

FIG. 4 and FIG. 8 show the state of execution of the V-groove formingprocess together with its apparatus.

In these drawings, the parts corresponding to those in FIG. 3 are givensame numerical codes (as to the units digit) in the order of 700s andare not specifically explained herein.

A rotary inner die 701 is smaller in diameter than the inner cavitydiameter of the cup-shaped blank 1 and possesses a plurality of V-grooveforming ridges 705a provided on a V-groove preliminary forming roller705 and corresponding plural ridges 701a, and the V-groove preliminaryforming roller 705 collaborates with said upper pressing die 704 to forma plurality of V-grooves 2 in a multiple arrangement, keeping aspecified interval, in the thickened peripheral wall 14 of thecup-shaped blank 1.

In this process, the upper pressing die 704 does not apply compressiveaction to the peripheral wall 14, and it is used to hold the cup-shapedblank 1 in collaboration with the rotary inner die 701. Accordingly,only rolling process is applied, and as a result, since a die possessinga plurality of ridges 701a as shown in the drawing may be used as therotary inner die 701, folds 9 may be prevented when forming V-grooves bypressing the V-groove auxiliary forming roller 705 to the rotary innerdie 701 and squeezing or pressing the thickened peripheral wall 14 bymeans of V-groove forming ridges 705a and ridges 701a. Therefore, evenafter manufacture of poly-V pulley, remaining of folds as shown in FIG.17 in the bottoms between poly-V grooves 3 may be prevented.

FIG. 5 and FIG. 9 show the state of execution of finishing process, thatis, the process of forming poly-V-grooves, together with its apparatus.

In these drawings, the parts corresponding to those in FIG. 3 are givensame numerical codes in the order of 800s.

The rotary inner die 801 is smaller in diameter than the inner cavity ofthe cup-shaped blank 1, like the one used in the above V-groove formingprocess, and, as is more explicitly shown in FIG. 9, it possesses pluralridges 801a corresponding to a plurality of ridges 805a of finishingroller 805. Such rotary inner die 801 collaborates with the finishingroller 805 to roll the plural V-grooves 2 formed in the peripheral wallof the cup-shaped blank 1 more deeply so as to form poly-V grooves 3 ofa desired shape.

This process is also, similar to said V-groove forming process, iseffected only by the rolling process.

In this manner, deep poly-V grooves 3 to be engaged with the ridges of apoly-V belt are formed in the peripheral wall of the cup-shaped blank 1,and a sheet metal made poly-V pulley as shown in FIG. 1e ismanufactured.

FIG. 10a to FIG. 10f show an example of improvement of the manufacturingprocess preferably adopted in the manufacture of sheet metal made poly-Vpulley by applying this invention.

In these drawings, the parts corresponding to those in FIG. 1 are givensame numerical codes. Numeral 15 shows the peripheral wall of corrugatedcup-shaped blank.

As shown in these drawings, according to this method of improvement, anauxiliary forming process to corrugate the thickened peripheral wall 14of the cup-shaped blank 1 by the rolling process in collaboration withrotary inner die and pressing roller (of which apparatus is not shown)is provided before the V-groove forming process, as shown in FIG. 10f,so that grooves 15a having moderate bottoms corresponding to theV-grooves to be formed in the next process are formed in the peripheralwall 14 of the thickened cup-shaped blank 1.

Thus, when the thickened peripheral wall 14 is corrugated beforeV-groove forming process, the working time may be shortened as comparedwith the process where V-grooves are formed by one stroke. That is, ifit is attempted to form V-grooves 2 as shown in FIG. 10d in a shorttime, each protrusion 2a formed between V-grooves 2, 2 comes toforcefully press the bottoms 705b (see FIG. 8) of the V-groovepreliminary forming roller 705, which may give rise to, in a worst case,cracks in the bottoms 705b or even breakage of the roller 705. To avoidsuch troubles, it is necessary to forward the V-groove preliminaryforming roller 705 gradually to press and transform the thickenedperipheral wall 14 slowly, which requires a long time of work in spiteof the less number of processes. To the contrary, when the corrugatingprocess is added the above troubles are sufficiently avoided althoughthe number bf processes is increased, and the total working time isshortened on the whole. Thus, along with the automation of the equipmentitself, V-grooves may be formed in a short time.

Moreover, by adding said corrugating process, since the peripheral wallcan be securely plastically transformed to a desired shape in thesubsequent V-groove forming process and finishing process, the lower endopening of the finished sheet metal made poly-V pulley is not widened(in the shape of an unfolded fan) as experienced in the prior art, sothat a sheet metal made poly-V pulley excellent in the product precisionmay be obtained.

In the above embodiment, the peripheral wall 10 is uniformly increasedin thickness in the preliminary second process (thickening process),but, as shown in FIG. 11, for example the wall thickness may beincreased locally by building up thickness in the upper end and lowerend parts, while making the middle parts thinner.

Such locally thick structure brings about the following advantage. Thatis, while forming the peripheral wall in a desired shape in thecorrugating process, V-groove forming process and finishing process, thematerial flow is concentrated in the direction of the middle part of theperipheral wall making the middle part thicker than the upper and lowerparts, but when the thickness is added locally as mentioned above, evenif the material concentrates in the direction of middle part of theperipheral wall, the peripheral wall of the finished sheet metal madepoly-V pulley may be formed in a uniform thickness, so that themechanical strength of the sheet metal made poly-V pulley may beuniformly stabilized.

Such locally thickened structure may be achieved in the followingmethod.

As shown in FIGS. 12 and 13, instead of said auxiliary forming roller605, an auxiliary forming roller 605' having a pressing plane 605'b topress the peripheral wall formed in an arc plane projecting outward isused, and by pressing the peripheral wall on which said curvature part11a (or 11b or 11c) is formed, the upper and end parts are made thickerthan the middle part.

So far is the explanation about the embodiment in the first invention,and the embodiment in the second invention is described below.

In the embodiment of the second invention, what differs from theembodiment in said first invention lies in that the thickness is addedto the peripheral wall on which said curvature part 11a (or 11b or 11c)is formed, that the lug 13 is preliminarily formed, and that the firstgrooves 12 are simultaneously formed preliminarily as shown in FIG. 14.Therefore, the other forming processes are identical and are notexplained herein, and only the different portions are describedhereunder in conjunction with FIGS. 15 and 16. Numeral 601" is a rotaryinner die which is inserted into the inner cavity of a cup-shaped blank1 to support the inner wall thereof, and this inner die 601" is affixedto a lower support die 602", and during the execution of this process,by rotating a turntable 603" affixed in the lower part of the lowersupport die 602", it rotates while holding and fixing the cup-shapedblank 1 in collaboration with an upper pressing die 604" having aconcave part 604"a.

Numeral 605" denotes an auxiliary forming roller used in forming a lug13 and a first groove 12 in the peripheral wall of the cup-shapedblank 1. This roller 605", as is more explicitly shown in FIG. 16, iscomposed of a concave part 605"a for forming the lug 13 in thecup-shaped blank 1 and a ridge 605"b for preliminarily forming the firstgroove 12, and it collaborates with the upper pressing die 604" tocompress said rotary inner die 601" and cup-shaped blank 1 from above inthe axial direction, and increases the thickness of the peripheral wallof the cup-shaped blank 1 on which curvature part 11a (or 11b or 11c) isformed while preliminarily forming the first groove 12 on the peripheralwall of the cup-shaped blank 1. In other words, in this process, thecup-shaped blank 1 is subjected to the compression in the axialdirection by means of upper pressing die 604", and by the simultaneousapplication of both compression and rolling in coordination of therotary motion of rotary inner die 601" and advancing motion of auxiliaryforming roller 605", the blank 1 comes to be formed into a shape asshown in FIG. 14.

When the first groove 12 is preliminarily formed in thickened peripheralwall, in the subsequent V-groove forming process where the uppermostside ridge 705a of the V-groove preliminary forming roller 705 ispressed and inserted into this first groove (see FIG. 8), the individualdownward V-grooves 2 are formed on the basis of this first groove 12, sothat the fluctuations in the accuracy between the V-grooves 2 may bealmost completely eliminated. As a result, a sheet metal made poly-Vpulley with advanced product precision may be manufactured.

Also in this embodiment of the second invention, it is further possibleto install the corrugating process before the V-groove forming process,or employ the locally thickened structure, as attempted in theembodiment of the first invention stated above.

The corrugating process may be added, meanwhile, by pressing andinserting the uppermost side ridge of the peripheral wall pressingroller to be used in the corrugation process to the first groove. As aresult, the corrugation forming may be effected precisely, and thesubsequent V-groove forming process and finishing process may beperformed also at high precision.

What is claimed is:
 1. A method of manufacturing sheet metal made poly-Vpulleys with poly-V grooves having a uniform thickness which comprisesthe steps of:forming a curvature on a peripheral wall of a cup-shapedblank, prior to any lug formation; after said forming step,preliminarily forming a lug on the peripheral wall of said cup-shapedblank with the curvature, and simultaneously thickening said peripheralwall by pressing radially against the peripheral wall on which saidcurvature has been formed by means of an auxiliary forming rollerpossessing a lug forming concave part while holding the inner wall ofthe cup-shaped blank with a rotary inner die, rotating the cup-shapedblank and confining the blank in the radial direction; and then, forminga plurality of V-grooves in a multiple arrangement on the thickenedperipheral wall by squeezing between a V-groove preliminary formingroller possessing a plurality of V-groove forming ridges located at theouter side of the peripheral wall and a rotary inner die possessing aplurality of ridges located at the inner side of the peripheral wallwhile rotating the cup-shaped blank; and, forming poly-V grooves bypressing a finishing roller possessing a plurality of finishingV-grooves to said plurality of V-grooves while rotating the cup-shapedblank.
 2. A method of manufacturing sheet metal made poly-V pulleys asset forth in claim 1, wherein before pressing the thickened peripheralwall by said V-groove preliminary forming roller, the thickenedperipheral wall is preliminarily corrugated by pressing with a V-grooveforming auxiliary roller while rotating the cup-shaped blank, and theV-groove preliminary forming roller is pressed against each corrugatedbottom while rotating the cup-shaped blank.
 3. A method of manufacturingsheet metal made poly-V pulleys as set forth in claim 1 or 2, whereinsaid curvature is bent and formed in such a manner as to project theperipheral wall of the cup-shaped blank outward.
 4. A method ofmanufacturing sheet metal made poly-V pulleys as set forth in claim 1 or2, wherein the pressing plane of said auxiliary forming roller to pressthe peripheral wall is formed in an outward projecting arc plane, andthe peripheral wall on which said curvature has been formed is pressedby said auxiliary forming roller to thicken the peripheral wall of thecup-shaped blank in such a manner that the upper and lower end parts arethicker than the middle part.
 5. A method of manufacturing sheet metalmade poly-V pulleys with poly-V grooves having a uniform thickness whichcomprises the steps of:forming a curvature on a peripheral wall of acup-shaped blank, prior to any lug formation; after said forming step,preliminarily forming a lug and a first groove in said peripheral wallof the cup-shaped blank with the curvature and simultaneously thickeningthe peripheral wall by pressing radially against the peripheral wall onwhich said curvature has been formed by means of an auxiliary formingroller possessing a lug forming concave part and a first groovepreliminary forming ridge located beneath said lug forming concave partwhile hilding the inner wall of the cup-shaped blank with a rotary innerdie, rotating the cup-shaped blank and confining the blank in the axialdirection; and then, forming a plurality of V-grooves in a multiplearrangement in the thickened peripheral wall by means of a V-groovepreliminary forming roller possessing a plurality or V-groove formingridges located at the outer side of the peripheral wall and a rotaryinner die possessing a plurality of ridges located at the inner side ofthe peripheral wall while rotating the cup-shaped blank; and, formingpoly-V grooves by pressing a finishing roller possessing a plurality offinishing V-grooves against said plurality of V-grooves while rotatingthe cup-shaped blank whereby a uniform thickness of the peripheral wallis provided.
 6. A method of manufacturing sheet metal made poly-Vpulleys as set forth in claim 5, wherein before pressing the thickenedperipheral wall with said V-groove preliminary forming roller, theperipheral wall is corrugated by pressing with the V-groove auxiliaryforming roller while rotating the cup-shaped blank, and the V-groovepreliminary forming roller is pressed against each corrugated bottomwhile rotating the cup-shaped blank.
 7. A method of manufacturing sheetmetal made poly-V pulleys as set forth in claim 5 or 6, wherein thepressing plane of said auxiliary forming roller to press the peripheralwall is formed in an outward projecting arc plane, and the peripheralwall on which said curvature has been formed is pressed by saidauxiliary forming roller to thicken the peripheral wall of thecup-shaped blank in such a manner that the upper and lower end parts arethicker than the middle part.
 8. A method of manufacturing sheet metalmade poly-V pulleys as set forth in claim 5 or 6, wherein said curvatureis bent and formed in such a manner as to project the peripheral wall ofthe cup-shaped blank outward.